Method of producing advertising signs of smoke in the air



April 8, 19240 J. C. SAVAGE METHOD OF PRODUCING ADVERTISING SIGNS OF SMOKE IN THE AIR Filed Aux. 51. 1923 Jfinwfld'av e INVENTOR BY z.

ATTORNEY.

Patented Apr. 8, 1924.

JOHN c. SAVAGE, or NEW YORK, N. Y.

METHOD OF PRODUCING ADVERTISING SIGNS SMOKE IN THE AIR Application filed August 31, 1928. Serial No. 660,447.

To all whom it may concern:

Be it known that I, JOHN C. SAVAG a subject of the Kin of Great Britain, an a resident of New ork, county and State of New .York, have invented a certain new and useful Method of, Producing Advertising Signs of Smoke in the Air, of which the fol owing is a specification.

My invention relatesto the production of combinations of letters or words of smoke. in the air and of such character and per--'- sistence as to form advertising signs visible with the naked-eye by persons on the earth, and it has for its particular object the provision of a method bymeans of which such signs may be produced rapidly, accurately, and in form and position to remain visible for a substantiahperiod of time.

' Reference will be had to the accompanying drawing in which Fig. 1 is a side elevation of an aeroplane illustrating certain elements of the smoke forming apparatus.

Fig. 2 is a diagrammatic lan view illustrating an advertising sign rom above and the path of the aeroplane by means of which the sign is written by the laying of smoke. Fig. 3 is a diagram illustrating the determination of the height at which the sign is written.

Fig. 4 is a diagram illustrating methods of staggering succeeding letters.

Fig. 5 is a diagrammatic view illustrating the formation of that part of a letter comprising a sharp angle. In practicing my method, I may employ any suitable smoke forming devices on the aeroplane, such as the exhaust pipe extension 1 of themotor A, the supply tank 2 for the smoke forming chemical, the pipe 3 leading from the supply tank to the exhaust pipe, and the valve 4 for controlling the passage of the chemical to the exhaust pipe. In this form of apparatus the smoke forming substance may be a liquid convertible into a dense vapor by the heat of the exhaust gases. It will be understood, however, that any suitable smoke forming substances may be employed including those having a reaction or operable in the absence of applied heat.

In the writing of signs composed of combinations of letters I form the letters substantially in a horizontal plane or horizontal lanes and write .the letters backward, that is to say from right to left.

In Fig. of the drawings I have shown,

for purposes of illustration, 9. plan view of the sign Lucky Strike produced by my method. In the Writing of this sign the aeroplane, equipped with the smoke forming apparatus is driven to the selected altitude for the production of the sign and a feature of the present method relates to this step.

Air disturbances of all kinds such as cross-currents, gusts and other irregular movements of the air, tend to have a destructive effect upon the signs when produced, and also impede their production, although a steady substantial uni-directional movement of the air is not an ad-' verse factor. The air conditions at substantial distances from the ground are not indicated by those conditions on the ground. It may be that on the ground the wind is blowing in one direction while at 10,000 feet the direction may be at right angles thereto or even directly opposite. Cross air currents or gusts may be prevalent at a iven elevation and be absent in a higher or ower elevation. In my method I select the altitude for production of the sign by gradually increasing the altitude of the plane while observing a thermometric indicator. For the first few thousand feet of climb the air temperature decreases sometimes regularly per 1000 feet of climb and sometimes irregularly, such changes in temperature giving rise to convection currents in the air causing turbulence which is detrimental to the persistence of the sign. When, how-. ever, an altitude has been reached at which the thermometer remains constant or substantially so, the plane has entered an air stratum which is free from convection currents and turbulence, although there may be a steady wind in one direction. 'This altitude will be such distance from the ground as to be free of any mechanical air turbulence set up by the passage of the air over geographical or other obstructions on the ground.

' An example of the method of determining the altitude for writing the sign is illuscurring until above 12,000 feet. The selected altitude therefore would be between a 10,000 and 12,000 feet, preferably at 11,000

feet. Inasmuch as a sign of the length of that illustrated in Fig. 1 may be produced in approximately six minutes, it may be taken as an average condition that the selected stratum will not materially change during the production of the sign.

Having determined the tranquil air stratum, the pilot proceeds with the produc tion of the sign. Referring to Fig. 1, it will be seen that the pilot starts with the first letter of the sign, but that letter is placed on the extreme right pf the sign viewed from the position of writing. For convenience of formation, the pilot flies the plane in a straight line, whilst liberating a trail of dense persistently visible material, to form the lower bar of the letter L, at the end of the bar he shuts off the visible trail (at the beginning of the dotted line) and turns in a loop at the end of which he turns on the visible trail to form the angular connecting bar which completes the letter L. The U is then formed, and at the top of the left hand bar of the letter the pilot turns in a gradual reverse curve to a position at the base and substantially to the left of the U and he then reverses the curve to form the C, and so on, as indicated in Fig. 1, to the completion of the sign. The path of the plane along the lines of the individual letters I term the transcribing path and intermediate the letters the positionin path. When the plane reaches a positioning path the visible trail will be shut off, to be immediately turned on when the plane again reaches the transcribing path.

To assist the proper formation and positioning of the successive letters my method contemplates staggering one letter relatively to a preceding letter, as indicated in Fig. 4. In other words one letter is written at a distance either moderately above or below, the preceding letters. This enables the pilot to better gauge parallelism and termination points of a preceding letter, while the effect from the ground is exactly the same as when the letters are written in the same plane. Sixty feet may be considered as an example of the difierence in height between the letters in their staggered formation. It will be understood that the staggered formation of the letters while not an essential element of the method is a step which greatly assists the successful practice thereof.

In some cases in the formation of that art of a letter comprising a sharp angle, suc as the joining of the two bars forming the letter L, it is desirable, for example in conserving time, to avoid the positioning loop indicated by the dotted lines in Fig. 1. In the ordinary turning of the aeroplane the rudder controls are partially and gradually swung to im art a corresponding turn of the plane, the.p ane thus transcribing a curvilinear path. I have found that the pilot, at the approach of the jointure of the angular lines, suddenly throws the rudder controls all the way over, the nose of the plane will sharply swing to the desired direction while the tail of the plane will continue its movement in substantially a straight line until the nose has reached such position that the entire plane has turned at right angles. Thus throughout this operation the emission of the trail producing material may go on, conserving the lapse of time incurred by the positioning movement which is avoided. There are also cases in which, due to the position of preceding letters or a part of the letter comprising the angle, a positioning movement would be impracticable because the movements of the plane across or adjacent to the previously formed trail of visible material would tend to malform or even erase a portion of the trail. This condition is present in the small letter '1' shown in the word Strike, Fig. 2.

Having described my invention what I claim and desire to secure by Letters Patent is as follows 1. The method of forming advertising signs comprising combinations of letters by means of an aeroplane whilst emitting therefrom a trail of persistently visible material, which consists in'producing the first letter at the extreme ri ht of the sign, viewed from above, by fiyin 1n the backward outline of said letter in su stantially a horizontal plane whilst emitting the visible material, positioning the aeroplane to the left of the said letter and producin each of the successive letters by backwar substantially horizontal transcription.

2. In themethod specified in claim 1, the production of successive letters at varying heights, for the purpose described.

3. In the method specified in claim 1, the joining of angular lines in a letter by shut ting off the visible material at the end of a line and looping the aeroplane until its flight is in the desired angular line and thereupon turning on the visible material.

4. The method of forming advertising signs comprising combinations of letters in the air by means of an aeroplane whilst emitting therefrom a trail of persistently visible material, which consists in increasing the altitude of the aeroplane from the ground level whilst observing temperature changes in the air, determining a relativel tranquil air stratum by a condition of re atively fixed temperature therein, and in said stratum flying in the backward outline of the letters whilst emitting the visible material.

5. In the method specified in claim 1 the forming of corners of letters by suddenly are from a trail of persistently visible material,

which consists in flying the aeroplane in the backward outline of each letter in substantially a horizontal plane whilst emitting the visible material.

Signed at New York, county and State of New York, this 21st da of Au J AVAGE. v 

